The main objective is to evaluate the bronchodilatory efficacy, safety and pharmacokinetic profiles of A006 (Albuterol Dry Powder Inhaler (DPI)), in comparison with those of an active control, Proventil-HFA (Albuterol Metered Dose Inhaler (MDI)), and a Placebo DPI in escalating and cumulative-doses up to 1440 mcg, eight (8) times of the proposed clinical dose.